[RTEMS Project] #3459: Rework initialization and interrupt stack support

[RTEMS trac]

#3459: Rework initialization and interrupt stack support
-----------------------------+------------------------------
 Reporter:  Sebastian Huber  |       Owner:  Sebastian Huber
     Type:  enhancement      |      Status:  assigned
 Priority:  normal           |   Milestone:  5.1
Component:  score            |     Version:  5
 Severity:  normal           |  Resolution:
 Keywords:                   |  Blocked By:
 Blocking:  3433             |
-----------------------------+------------------------------

Comment (by Sebastian Huber <sebastian.huber@…>):

 In [changeset:"511dc4b2bee78ce0714e83838644429a29d325b1/rtems"
 511dc4b/rtems]:
 {{{
 #!CommitTicketReference repository="rtems"
 revision="511dc4b2bee78ce0714e83838644429a29d325b1"
 Rework initialization and interrupt stack support

 Statically initialize the interrupt stack area
 (_Configuration_Interrupt_stack_area_begin,
 _Configuration_Interrupt_stack_area_end, and
 _Configuration_Interrupt_stack_size) via <rtems/confdefs.h>.  Place the
 interrupt stack area in a special section ".rtemsstack.interrupt".  Let
 BSPs define the optimal placement of this section in their linker
 command files (e.g. in a fast on-chip memory).

 This change makes makes the CPU_HAS_SOFTWARE_INTERRUPT_STACK and
 CPU_HAS_HARDWARE_INTERRUPT_STACK CPU port defines superfluous, since the
 low level initialization code has all information available via global
 symbols.

 This change makes the CPU_ALLOCATE_INTERRUPT_STACK CPU port define
 superfluous, since the interrupt stacks are allocated by confdefs.h for
 all architectures.  There is no need for BSP-specific linker command
 file magic (except the section placement), see previous ARM linker
 command file as a bad example.

 Remove _CPU_Install_interrupt_stack().  Initialize the hardware
 interrupt stack in _CPU_Initialize() if necessary (e.g.
 m68k_install_interrupt_stack()).

 The optional _CPU_Interrupt_stack_setup() is still useful to customize
 the registration of the interrupt stack area in the per-CPU information.

 The initialization stack can reuse the interrupt stack, since

   * interrupts are disabled during the sequential system initialization,
     and

   * the boot_card() function does not return.

 This stack resuse saves memory.

 Changes per architecture:

 arm:

   * Mostly replace the linker symbol based configuration of stacks with
     the standard <rtems/confdefs.h> configuration via
     CONFIGURE_INTERRUPT_STACK_SIZE.  The size of the FIQ, ABT and UND
     mode stack is still defined via linker symbols.  These modes are
     rarely used in applications and the default values provided by the
     BSP should be sufficient in most cases.

   * Remove the bsp_processor_count linker symbol hack used for the SMP
     support. This is possible since the interrupt stack area is now
     allocated by the linker and not allocated from the heap.  This makes
     some configure.ac stuff obsolete.  Remove the now superfluous BSP
     variants altcycv_devkit_smp and realview_pbx_a9_qemu_smp.

 bfin:

   * Remove unused magic linker command file allocation of initialization
     stack.  Maybe a previous linker command file copy and paste problem?
     In the start.S the initialization stack is set to a hard coded value.

 lm32, m32c, mips, nios2, riscv, sh, v850:

   * Remove magic linker command file allocation of initialization stack.
     Reuse interrupt stack for initialization stack.

 m68k:

   * Remove magic linker command file allocation of initialization stack.
     Reuse interrupt stack for initialization stack.

 powerpc:

   * Remove magic linker command file allocation of initialization stack.
     Reuse interrupt stack for initialization stack.

   * Used dedicated memory region (REGION_RTEMSSTACK) for the interrupt
     stack on BSPs using the shared linkcmds.base (replacement for
     REGION_RWEXTRA).

 sparc:

   * Remove the hard coded initialization stack.  Use the interrupt stack
     for the initialization stack on the boot processor.  This saves
     16KiB of RAM.

 Update #3459.
 }}}

--
Ticket URL: <http://devel.rtems.org/ticket/3459#comment:11>
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